Impacts of livestock grazing on a savanna grassland in Kenya

The dynamics of most rangelands in Kenya remain to be poorly understood. This paper provides baseline information on the response of a semiarid rangeland under different livestock grazing regimes on land inhabited by the Massai people in the east side of Amboseli National Park in Kenya. The data were collected from grasslands designated into four types： （1） grassland from previous Massai settlements that had been abandoned for over twenty years; （2） grassland excluded from livestock grazing for eight years; （3） a dry season grazing area; and （4） a continuous grazing area where grazing occurred throughout all seasons. Collected data included grass species composition, grass height, inter-tuft distance, standing grass biomass and soil characteristics. The results indicated that continuous grazing area in semiarid rangelands exhibited loss of vegetation with negative, long-term effects on grass functional qualities and forage production, whereas grassland that used traditional Maasai grazing methods showed efficiency and desirable effects on the rangelands. The results also showed that abandoned homestead sites, though degraded, were important nutrient reservoirs.

Long-term light grazing does not change soil organic carbon stability and stock in biocrust layer in the hilly regions of drylands

Livestock grazing is the most extensive land use in global drylands and one of the most extensive stressors of biological soil crusts(biocrusts).Despite widespread concern about the importance of biocrusts for global carbon(C)cycling,little is known about whether and how long-term grazing alters soil organic carbon(SOC)stability and stock in the biocrust layer.To assess the responses of SOC stability and stock in the biocrust layer to grazing,from June to September 2020,we carried out a large scale field survey in the restored grasslands under long-term grazing with different grazing intensities(represented by the number of goat dung per square meter)and in the grasslands strictly excluded from grazing in four regions(Dingbian County,Shenmu City,Guyuan City and Ansai District)along precipitation gradient in the hilly Loess Plateau,China.In total,51 representative grassland sites were identified as the study sampling sites in this study,including 11 sites in Guyuan City,16 sites in Dingbian County,15 sites in Shenmu City and 9 sites in Ansai District.Combined with extensive laboratory analysis and statistical analysis,at each sampling site,we obtained data on biocrust attributes(cover,community structure,biomass and thickness),soil physical-chemical properties(soil porosity and soil carbon-to-nitrogen ratio(C/N ratio)),and environmental factors(mean annual precipitation,mean annual temperature,altitude,plant cover,litter cover,soil particle-size distribution(the ratio of soil clay and silt content to sand content)),SOC stability index(SI)and SOC stock(SOCS)in the biocrust layer,to conduct this study.Our results revealed that grazing did not change total biocrust cover but markedly altered biocrust community structure by reducing plant cover,with a considerable increase in the relative cover of cyanobacteria(23.1%)while a decrease in the relative cover of mosses(42.2%).Soil porosity and soil C/N ratio in the biocrust layer under grazing decreased significantly by 4.1%–7.2%and 7.2%–13.3%,respectively,compared with those under grazing exclusion.The shifted biocrust community structure ultimately resulted in an average reduction of 15.5%in SOCS in the biocrust layer under grazing.However,compared with higher grazing(intensity of more than 10.00 goat dung/m2),light grazing(intensity of 0.00–10.00 goat dung/m2 or approximately 1.20–2.60 goat/(hm2•a))had no adverse effect on SOCS.SOC stability in the biocrust layer remained unchanged under long-term grazing due to the offset between the positive effect of the decreased soil porosity and the negative effect of the decreased soil C/N ratio on the SOC resistance to decomposition.Mean annual precipitation and soil particle-size distribution also regulated SOC stability indirectly by influencing soil porosity through plant cover and biocrust community structure.These findings suggest that proper grazing might not increase the CO_(2) release potential or adversely affect SOCS in the biocrust layer.This research provides some guidance for proper grazing management in the sustainable utilization of grassland resources and C sequestration in biocrusts in the hilly regions of drylands.

Understanding sheep baa-haviour: Investigating the relationship between pasture and animal grazing patterns

Background:Grasslands are the primary source of feed for grazing livestock,and as such,knowledge on how to best manage livestock and grasslands,through the use of spatiotemporal modelling,will assist in the long-term management of a valuable ecosystem resource.Methods:This study was conducted over 14 months between March and April 2017 in Orange,NSW,Australia.The study evaluated sheep behaviour in relation to the presence of pasture species,environment and paddock structures,using random forest modelling,to predict sheep location under continuous high(HSR,13 DSE ha−1)and low(LSR,7DSE ha−1)stocking rates.Results:In the LSR,significant drivers included water,shade and fence lines(p<0.01).In the HSR,only fence lines and available biomass were found to be significant(p<0.01).The presence of green legumes in both stocking rates often increased residency by sheep.Animals spent more time together in the LSR,suggesting that social behaviour played a larger role than pasture quantity and quality in driving grazing behaviours.Conclusions:Understanding how pasture type can influence grazing behaviours and also how animal behaviour affects pasture performance and utilisation is important in developing long-term sustainable management strategies on a paddock scale.

Thermoregulatory value of cracking-clay soil shelters for small vertebrates during extreme desert conditions

Deserts exhibit extreme climatic conditions.Small desert-dwelling vertebrates have physiological and behavioral adaptations to cope with these conditions,including the ability to seek shelter.We investigated the temperature(T)and relative humidity(RH)regulating properties of the soil cracks that characterize the extensive cracking-clay landscapes of arid Australia,and the extent of their use by 2 small marsupial species:fat-tailed and stripe-faced dunnarts(Sminthopsis crassicaudata and Sminthopsis macroura).We measured hourly(over 24-h periods)the T and RH of randomly-selected soil cracks compared to outside conditions,during 2 summers and 2 winters.We tracked 17 dunnarts(8 Sminthopsis crassicaudata and 9 Sminthopsis macroura)to quantify their use of cracks.Cracks consistently moderated microclimate,providing more stable conditions than available from non-crack points,which often displayed comparatively dramatic fluctuations in T and RH.Both dunnart species used crack shelters extensively.Cracks constitute important shelter for small animals during extreme conditions by providing a stable microclimate,which is typically cooler than outside conditions in summer and warmer in winter.Cracks likely play a fundamental sheltering role by sustaining the physiological needs of small mammal populations.Globally,cracking-clay areas are dominated by agricultural land uses,including livestock grazing.Management of these systems should focus not only on vegetation condition,but also on soil integrity,to maintain shelter resources for ground-dwelling fauna.

Kin recognition benefits clonal offspring performance of historically grazed Leymus chinensis:insights for grassland management

Background:Individual plants can identify their neighbors and adjust their biomass investment to avoid competing with their relatives or jointly cope with external stresses.Maternal effects can improve their offspring adaptability under external stresses.However,how grazing-induced maternal effects influence plant kin interactions remain unknown.Methods:Clonal offspring of Leymus chinensis grown under multi-year grazing and non-grazing conditions were used for this study.A greenhouse experiment was conducted to evaluate the performance of focal plants in the presence of kin and stranger neighbors,with the aim of analyzing the interaction between maternal effect and kin relatedness.Results:Kin relatedness of neighboring plants affected the biomass production and allocation of focal plants,demonstrating the presence of kin recognition in L.chinensis.Moreover,grazing-induced maternal effects significantly enhanced kin recognition in the species.Consequently,the presence of stranger neighbors significantly improved the growth potential of grazed offspring.Specifically,the total biomass of clonal offspring increased by 73.1%compared to the kin group,potentially buffering grazing-induced plant productivity declines.Conclusions:This study shows that historical grazing enhances kin recognition in L.chinensis.Thus,introducing multi-genotypic plants can increase the productivity of grasslands.The findings of this study enhance our understanding of intraspecific plant–plant interactions in clonal species and provide new insights into sustainable grassland management.

Alien plant species coexist over time with native ones in Chilean Mediterranean grasslands

Aims Alien species are commonly considered as harmful weeds capa-ble of decreasing native biodiversity and threatening ecosystems.Despite this assumption,little is known about the long-term patterns of the native-alien relationships associated with human disturbed managed landscapes.This study aims to elucidate the commu-nity dynamics associated with a successional gradient in chilean Mediterranean grasslands,considering both native and alien species.Methods Species richness(natives and aliens separately)and life-form(annu-als and perennials)were recorded in four chilean post-agricultural grazed grasslands each covering a broad successional gradient(from 1 to 40 years since crop abandonment).A detrended correspondence analysis(DcA),mixed model effects analyses and cor-relation tests were conducted to assess how this temporal gradient influenced natives and aliens through community dynamics.Important Findings Our results show different life-form patterns between natives and aliens over time.Aliens were mainly represented by annuals(especially ruderals and weeds),which were established at the beginning of succession.Annual aliens also predominated at mid-successional stages,but in old grasslands native species were slightly more representative than alien ones within the community.In the late successional states,positive or no correlations at all between alien and native species richness suggested the absence of competition between both species groups,as a result of differ-ent strategies in occupation of the space.community dynamics over time constitute a net gain in biodiversity,increasing natives and maintaining a general alien pool,allowing the coexistence of both.Biotic interactions including facilitation and/or tolerance processes might be occurring in chilean post-agricultural grasslands,a fact that contradicts the accepted idea of the alien species as contenders.

Carbon dioxide exchange and biomass productivity of the herbaceous layer of a managed tropical humid savanna ecosystem in western Kenya

Aims Humid savannas,as a result of high precipitation amounts,are highly productive.they are also hotspots for land use change and potential sources of carbon dioxide(CO_(2))due to the large soil carbon(C)stocks.understanding how ecosystem CO_(2) exchange is influenced by changes arising from agricultural land use is vital in future management of these ecosystems and in responding to the ongoing shifts in manage-ment and climate.the aim of this study was to identify how ecosystem CO_(2) exchange and biomass productivity of the herbaceous layer of a humid savanna in Kenya respond to current management practices.Methods We used flux chambers to quantify CO_(2) fluxes,while monthly harvests were undertaken to determine biomass development of the herba-ceous layer of three sites that were(i)fenced to exclude livestock graz-ing,(ii)subjected to grazing by livestock and(iii)abandoned after being cultivated for maize production and also open to grazing by livestock.Important findingsthe peak aboveground biomass ranged between 380 and 1449 g m−2 and biomass production was significantly(P<0.05)lower in the grazed and abandoned plots.the maximum gross primary production(gPP)and net ecosystem CO_(2) exchange(NEE)ranged between 21.8±1.3 to 32.5±2.7 and−9.6±0.7 to−17.9±4.8μmol m−2 s−1,respectively.seasonal NEE fluctuations ranged between 10 and 21μmol m−2s−1,while spatial(among sites)differences ranged between 2 and 10μmol m−2 s−1.Ecosystem respiration(Reco)fluc-tuated between 5 and 10μmol m−2 s−1 during the growing sea-son.Reco was,however,not significantly different among the sites.unlike in other similar ecosystems where ecosystem respiration is determined by the ambient temperature,we did not find any rela-tionship between Reco and temperature in this savanna.Instead,soil moisture accounted for 38-88%of the spatial and seasonal fluc-tuations in ecosystem CO_(2) fluxes and aboveground biomass pro-duction.management influenced the maximum gPP and NEE rates through modification of soil moisture,plant species composition and aboveground biomass.We concluded that soil moisture is the key determinant of ecosystem CO_(2) exchange and productivity in this tropical savanna.management,however,significantly modifies C fluxes and productivity through its influence on soil moisture,plant species composition and aboveground green biomass and should be taken into consideration in future similar studies.